What additive increases the overall flexibility and life of a coating?

The correct response is beneficial because rejuvenators are specifically formulated to enhance the flexibility and longevity of coatings. Over time, coatings can become brittle due to environmental exposure and aging. A rejuvenator effectively restores the original properties of the coating or enhances its flexibility, thus preventing cracking and extending the life of the finish.

When considering other additives: sealants primarily focus on protecting surfaces from moisture or corrosion but do not necessarily contribute to flexibility. Hardeners are designed to increase the durability and strength of a coating, which might compromise flexibility. Adhesives are meant for bonding layers together rather than modifying the properties of coatings. Therefore, selecting a rejuvenator is essential for maintaining the flexibility and lifespan of the coating material.